Multi-layered unit including electrode and dielectric layer

ABSTRACT

A multi-layered unit according to the present invention includes a support substrate formed of fused quartz, an electrode layer formed on the support substrate, made of BSCCO (bismuth strontium calcium copper oxide) having a stoichiometric composition represented by Bi 2 Sr 2 CaCu 2 O 8 , having an anisotropic property and conductivity and enabling epitaxial growth of a dielectric material containing a bismuth layer structured compound thereon and oriented in the c axis direction, and a dielectric layer formed by epitaxially growing a dielectric material containing a bismuth layer structured compound having a composition represented by SrBi 4 Ti 4 O 15  on the electrode layer. Since the thus constituted multi-layered unit includes the dielectric layer containing the bismuth layer structured compound oriented in the c axis direction, in the case of, for example, providing an upper electrode on the dielectric layer to form a thin film capacitor and applying a voltage between the electrode layer and the upper electrode, the direction of the electric field substantially coincides with the c axis of the bismuth layer structured compound. As a result, since the ferroelectric property of the bismuth layer structured compound contained in the dielectric layer can be suppressed and the paraelectric property thereof can be fully exhibited, it is possible to fabricate a thin film capacitor having a small size and large capacitance.

BACKGROUND OF THE INVENTION

The present invention relates to a multi-layered unit including anelectrode and a dielectric layer and, particularly, to a multi-layeredunit suitable for fabricating a thin film capacitor having a small size,large capacitance and an excellent dielectric characteristic andsuitable for fabricating an inorganic EL (electro-luminescence) devicecapable of emitting light having high luminescence.

DESCRIPTION OF THE PRIOR ART

Recently, the operating frequency of LSIs (Large Scale Integratedcircuits), typically CPUs (Central Processing Units), has become higherand higher. In the LSI having a high operating frequency, power supplynoise is very likely to be generated, and once power supply noiseoccurs, a voltage drop occurs due to parasitic resistance and parasiticinductance of the power supply wiring, causing the LSI to operateerroneously.

In order to prevent such a voltage drop caused by power supply noise, adecoupling capacitor is generally connected between the terminals of theLSI power supply. In the case where a decoupling capacitor is connectedbetween the terminals of the LSI power supply, the impedance of thepower supply wiring decreases to effectively prevent voltage drop causedby power supply noise.

The impedance required of the power supply wiring is proportional to theoperating voltage of the LSI and inversely proportional to theintegration density of the LSI, the switching current of the LSI and theoperating frequency of the LSI. Therefore, in current LSIs, which havehigh integration density, low operating voltage and high operatingfrequency, the impedance required of the power supply wiring isextremely low.

In order to achieve such low impedance of the power supply wiring, it isnecessary to increase the capacitance of the decoupling capacitor andconsiderably lower the inductance of the wiring connecting the terminalsof the LSI power supply and the decoupling capacitor.

As a decoupling capacitor having a large capacitance, an electrolyticcapacitor or a multilayer ceramic capacitor is generally employed.However, since the size of an electrolytic capacitor or multilayerceramic capacitor is relatively large, it is difficult to integrate itwith an LSI. Therefore, the electrolytic capacitor or multilayer ceramiccapacitor has to be mounted on a circuit substrate independently of theLSI and, as a result, the length of wiring for connecting the terminalsof the LSI power supply and the decoupling capacitor is inevitably long.Accordingly, in the case where an electrolytic capacitor or a multilayerceramic capacitor is employed as a decoupling capacitor, it is difficultto lower the inductance of the wiring for connecting the terminals ofthe LSI power supply and the decoupling capacitor.

In order to shorten the wiring for connecting the terminals of the LSIpower supply and the decoupling capacitor, use of a thin film capacitorhaving a smaller size than that of an electrolytic capacitor or amultilayer ceramic capacitor is suitable.

Japanese Patent Application Laid Open No. 2001-15382 discloses a thinfilm capacitor having a small size and large capacitance which employsPZT, PLZT, (Ba, Sr) TiO₃ (BST), Ta₂O₅ or the like as a dielectricmaterial.

However, the thin film capacitor employing any one of the abovementioned materials is disadvantageous in that the temperaturecharacteristic thereof is poor. For example, since the dielectricconstant of BST has a temperature dependency of −1000 to −4000 ppm/° C.,in the case where BST is employed as a dielectric material, thecapacitance of the thin film capacitor at 80° C. varies between −6% and−24% in comparison with that at 20° C. Therefore, a thin film capacitoremploying BST as a dielectric material is not suitable for use as adecoupling capacitor for a high operating frequency LSI whose ambienttemperature frequently reaches 80° C. or higher owing to heat generatedby electric power consumption.

Furthermore, the dielectric constant of a dielectric thin film formed ofany one of the above mentioned materials decreases as the thicknessthereof decreases and the capacitance thereof greatly decreases when anelectric field of 100 kV/cm, for example, is applied thereto. Therefore,in the case where any one of the above mentioned materials is used as adielectric material for a thin film capacitor, it is difficult tosimultaneously make the thin film capacitor small and the capacitancethereof great.

In addition, Moreover, since the surface roughness of a dielectric thinfilm formed of any one of the above mentioned materials is high, itsinsulation performance tends to be lowered when formed thin.

It might be thought possible to overcome these problems by using abismuth layer structured compound as a dielectric material for a thinfilm capacitor. The bismuth layer structured compound is discussed byTadashi Takenaka in “Study on the particle orientation of bismuth layerstructured ferroelectric ceramics and their application to piezoelectricor pyroelectric materials” Engineering Doctoral Thesis at the Universityof Kyoto (1984), Chapter 3, pages 23 to 36.

It is known that the bismuth layer structured compound has ananisotropic crystal structure and behaves as a ferroelectric materialbut that the bismuth layer structured compound exhibits only weakproperty as a ferroelectric material and behaves like as a paraelectricmaterial along a certain axis of orientation.

The property of the bismuth layer structured compound as a ferroelectricmaterial is undesirable when the bismuth layer structured compound isutilized as a dielectric material for a thin film capacitor since itcauses variation in dielectric constant. Therefore, when a bismuth layerstructured compound is used as a dielectric material for a thin filmcapacitor, it is preferable that its paraelectric property can be fullyexhibited.

Therefore, a need has been felt for the development of a thin filmcapacitor of small size, large capacitance and excellent dielectriccharacteristic that has a dielectric layer in which a bismuth layerstructured compound oriented in the axis of orientation along which thebismuth layer structured compound exhibits only weak property as aferroelectric material and behaves like a paraelectric material.

On the other hand, it is necessary in order to fabricate an inorganic EL(electro-luminescence) device for emitting light having highluminescence to provide a dielectric layer having a high insulatingproperty between an electrode and an inorganic EL device and it istherefore required to develop an inorganic EL device provided with adielectric layer in which a bismuth layer structured compound orientedin the axis of orientation along which the bismuth layer structuredcompound exhibits only weak property as a ferroelectric material andbehaves like a paraelectric material.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide amulti-layered unit suitable for fabricating a thin film capacitor havinga small size and large capacitance and suitable for fabricating aninorganic EL (electro-luminescence) device capable of emitting lighthaving high luminescence.

The above and other objects of the present invention can be accomplishedby a multi-layered unit constituted by forming on a support substrateformed of a material on which crystals cannot be epitaxially grown, anelectrode layer formed of a material having an anisotropic property andconductivity and enabling epitaxial growth of a dielectric materialcontaining a bismuth layer structured compound and oriented in the [001]direction, and a dielectric layer formed by epitaxially growing adielectric material containing a bismuth layer structured compound onthe electrode layer and oriented in the [001] direction in this order.

In the present invention, the [001] direction as termed herein means the[001] direction of a cubic crystal, a tetragonal crystal, a monocliniccrystal or an orthorhombic crystal.

According to the present invention, since the electrode layer is formedof a material having an anisotropic property and conductivity andenabling epitaxial growth of a dielectric material containing a bismuthlayer structured compound and oriented in the [001] direction, theelectrode layer can also serve as a buffer layer and a dielectric layercontaining a bismuth layer structured compound reliably oriented in the[001] direction can be formed by epitaxially growing a dielectricmaterial containing the bismuth layer structured compound on theelectrode layer.

Therefore, according to the present invention, since the c axis of thebismuth layer structured compound contained in a dielectric layer can beoriented so as to be perpendicular to the electrode layer, in the caseof, for example, providing an upper electrode on the dielectric layerand applying a voltage between the electrode layer and the upperelectrode, the direction of the electric field substantially coincideswith the c axis of the bismuth layer structured compound contained inthe dielectric layer. Accordingly, since the ferroelectric property ofthe bismuth layer structured compound can be suppressed and theparaelectric property thereof can be fully exhibited, it is possible tofabricate a thin film capacitor having a small size and largecapacitance.

Further, according to the present invention, since the dielectric layerof the dielectric material containing the bismuth layer structuredcompound whose c axis orientation is improved has a high insulatingproperty, it is possible to form the dielectric layer thinner andtherefore make a thin film capacitor much smaller.

Furthermore, since the dielectric layer of the dielectric materialcontaining the bismuth layer structured compound whose c axisorientation is improved has a high insulating property, it is possibleto cause an inorganic EL device to emit light in a desired manner andfabricate an inorganic EL device capable of emitting light having highluminescence by disposing the inorganic EL device on the dielectriclayer of the multi-layered unit according to the present invention,disposing another electrode on the inorganic EL device and applying avoltage between the electrode layer and another electrode.

In the present invention, the dielectric material containing the bismuthlayer structured compound may contain unavoidable impurities.

In the present invention, it is sufficient for the support substrate tobe formed of a material on which crystals cannot be epitaxially grownand the material for forming the support substrate is not particularlylimited. An amorphous substrate made of fused quartz or the like, apolycrystal substrate made of ceramic or the like, a heat-resistantglass substrate, a resin substrate or the like can be used as thesupport substrate.

In the present invention, the multi-layered unit includes an electrodelayer oriented in the [001] direction, namely, the c axis direction onthe support substrate.

In the present invention, the electrode layer is formed of a materialhaving an anisotropic property and conductivity and enabling epitaxialgrowth of a dielectric material containing a bismuth layer structuredcompound and is oriented in the [001] direction. Therefore, theelectrode layer serves as an electrode and a buffer layer for ensuringthat the dielectric layer containing a bismuth layer structured compoundoriented in the [001] direction, namely, the c axis direction, can beformed by epitaxially growing a dielectric material containing thebismuth layer structured compound thereon.

In the case of directly forming an electrode layer made of platinum orthe like on the support substrate made of fused quartz or the like,since the electrode layer tends to be oriented in the [111] direction,it is difficult to epitaxially grow a dielectric layer of a dielectricmaterial containing a bismuth layer structured compound on the electrodelayer and orient the bismuth layer structured compound in the [001]direction, namely, the c axis direction. However, in the presentinvention, since the electrode layer is formed of a material having ananisotropic property and conductivity and enabling epitaxial growth of adielectric material containing a bismuth layer structured compound, theelectrode can be oriented in the [001] direction and it is thereforepossible to form a dielectric layer by epitaxially growing a dielectricmaterial containing a bismuth layer structured compound on the electrodelayer and reliably orient the bismuth layer structured compoundcontained in the dielectric layer in the [001] direction, namely, the caxis direction.

In the present invention, the material for forming the electrode layeris not particularly limited insofar as it has an anisotropic propertyand conductivity and enables epitaxial growth of a dielectric materialcontaining a bismuth layer structured compound thereon, but an oxidesuperconductor is preferably used for forming the electrode layer.

Among oxide superconductors, a copper oxide superconductor having a CuO₂plane is more preferably used for forming the electrode layer.

Illustrative examples of a copper oxide superconductor having a CuO₂plane usable for forming the electrode layer include BSCCO (bismuthstrontium calcium copper oxide) represented by the stoichiometriccompositional formula: Bi₂Sr₂Ca_(n−1)Cu_(n)O_(2n+4) and YBCO (yttriumbarium copper oxide) represented by the stoichiometric compositionalformula: YBa₂Cu₃O_(7−δ).

In the present invention, it is not absolutely necessary for the degreeF of orientation in the [001] direction, namely, c axis orientation ofthe material having an anisotropic property and conductivity andcontained in the buffer layer to be 100% but it is sufficient for thedegree F of c axis orientation of the material to be equal to or morethan 80%. It is more preferable for the degree of c axis orientation ofthe material to be equal to or more than 90% and it is much morepreferable for the degree of c axis orientation of the material to beequal to or more than 95%.

The degree F of the c axis orientation of the material having ananisotropic property and conductivity is defined by the followingformula (1).F=(P−P₀)/(1−P₀)×100  (1)In formula (1), P₀ is defined as X-ray diffraction intensity ofpolycrystal whose orientation is completely random in the c axisdirection, namely, a ratio of the sum Σ I ₀(001) of reflectionintensities I₀ (001) from the surface of [001] of polycrystal whoseorientation is completely random to the sum Σ I₀ (hkl) of reflectionintensities I₀ (hkl) from the respective crystal surfaces of [hkl]thereof (Σ I ₀(001)/Σ I₀ (hkl)) and P is defined as X-ray diffractionintensity of the material having an anisotropic property andconductivity in the c axis direction, namely, a ratio of the sum Σ I(001) of reflection intensities I (001) from the surface of [001] of thematerial having an anisotropic property and conductivity to the sum Σ I(hkl) of reflection intensities I (hkl) from the respective crystalsurfaces of [hkl] thereof (Σ I (001)/Σ I (hkl)). The symbols h, k and lcan assume an arbitrary integer value equal to or larger than 0.

In the above formula (1), since P₀ is a known constant, when the sum Σ I(001) of reflection intensities I (001) from the surface of [001] of thematerial having an anisotropic property and conductivity and the sum Σ I(hkl) of reflection intensities I (hkl) from the respective crystalsurfaces of [hkl] are equal to each other, the degree F of the c axisorientation of the material having an anisotropic property andconductivity is equal to 100%.

In the present invention, the electrode layer can be formed using any ofvarious thin film forming processes such as a vacuum deposition process,a sputtering process, a pulsed laser deposition process (PLD), a metalorganic chemical vapor deposition process (MOCVD), a chemical solutiondeposition process (CSD process) such as a metal-organic decompositionprocess (MOD) and a sol-gel process or the like.

In the present invention, the multi-layered unit includes a dielectriclayer of a dielectric material containing a bismuth layer structuredcompound oriented in the [001] direction, namely, the c axis directionon the electrode layer.

In the present invention, a dielectric layer is formed by epitaxiallygrowing a dielectric material containing a bismuth layer structuredcompound on the electrode layer.

Since the dielectric layer is formed by epitaxially growing a dielectricmaterial containing a bismuth layer structured compound on the electrodelayer oriented in the [001] direction, it is possible to reliably orientthe bismuth layer structured compound contained in the dielectric layerin the [001] direction, namely, the c axis direction. Therefore, in thecase where a thin film capacitor is fabricated using the multi-layeredunit according to the present invention, since the bismuth layerstructured compound does not function as a ferroelectric material butfunctions as a paraelectric material, it is possible to incorporate athin film capacitor having a small size and large capacitance into asemiconductor wafer together with other devices.

As a bismuth layer structured compound for forming the dielectric layer,a bismuth layer structured compound having an excellent property as acapacitor material is selected.

The bismuth layer structured compound has a composition represented bythe stoichiometric compositional formula:(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ or Bi₂A_(m−1)B_(m)O_(3m+3), where thesymbol m is a natural number, the symbol A is at least one elementselected from a group consisting of sodium (Na), potassium (K), lead(Pb), barium (Ba), strontium (Sr), calcium (Ca) and bismuth (Bi), andthe symbol B is at least one element selected from a group consisting ofiron (Fe), cobalt (Co), chromium (Cr), gallium (Ga), titanium (Ti),niobium (Nb), tantalum (Ta), antimony (Sb), vanadium (V), molybdenum(Mo) and tungsten (W). In the case where the symbol A and/or B includestwo or more elements, the ratio of the elements can be arbitrarilydetermined.

As shown in FIG. 1, the bismuth layer structured compound has a layeredstructure formed by alternately laminating perovskite layers 1 eachincluding perovskite lattices 1 a made of (m−1) ABO₃ and (Bi₂O₂)²⁺layers 2.

The number of laminates each consisting of the perovskite layer 1 andthe (Bi₂O²)²⁺ layer 2 is not particularly limited and it is sufficientfor the bismuth layer structured compound to include at least one pairof (Bi₂O₂)²⁺ layers 2 and one perovskite layer 1 sandwichedtherebetween.

The c axis of the bismuth layer structured compound means the directionobtained by connecting the pair of (Bi₂O₂)²⁺ layers 2, namely, the [001]direction.

Among the bismuth layer structured compounds represented by the abovestoichiometric compositional formula, a bismuth layer structuredcompound having an excellent property as a capacitor material is usedfor forming the dielectric layer.

In the present invention, a bismuth layer structured compound forforming the dielectric layer is not particularly limited insofar as ithas an excellent property as a capacitor material but a bismuth layerstructured compound of the symbol m=4 in the above stoichiometriccompositional formula, namely, one that is represented by thestoichiometric compositional formula: (Bi₂O₂)²⁺ (A₃B₄O₁₃)²⁻ or Bi₂A₃B₄O₁₅ is preferably used because each of them has an excellent propertyas a capacitor material.

In the present invention, it is not absolutely necessary for the degreeF of orientation in the [001] direction, namely, c axis orientation ofthe bismuth layer structured compound to be 100% and it is sufficientfor the degree F of c axis orientation to be equal to or more than 80%.It is more preferable for the degree of c axis orientation of thebismuth layer structured compound to be equal to or more than 90% and itis much more preferable for the degree of c axis orientation of thebismuth layer structured compound to be equal to or more than 95%.

The degree F of the bismuth layer structured compound is defined by theformula (1).

The dielectric characteristic of a dielectric layer can be markedlyimproved by orienting the bismuth layer structured compound in the [001]direction, namely, the c axis direction in this manner.

More specifically, in the case where a thin film capacitor is fabricatedby forming, for example, an upper electrode on the dielectric layer ofthe multi-layered unit according to the present invention, even if thethickness of the dielectric layer is equal to or thinner than, forexample, 100 nm, a thin film capacitor having a relatively highdielectric constant and low loss (tan δ) can be obtained. Further, athin film capacitor having an excellent leak characteristic, an improvedbreakdown voltage, an excellent temperature coefficient of thedielectric constant and an excellent surface smoothness can be obtained.

In the present invention, it is particularly preferable that the bismuthlayer structured compound contained in the dielectric layer has acomposition represented by the stoichiometric compositional formula:Ca_(x)Sr_((1−x))Bi₄Ti₄O₁₅, where x is equal to or larger than 0 andequal to or smaller than 1. If the bismuth layer structured compoundhaving such a composition is used, a dielectric layer having arelatively large dielectric constant can be obtained and the temperaturecharacteristic thereof can be further improved.

In the present invention, parts of the elements represented by thesymbols A or B in the stoichiometric compositional formula of thebismuth layer structured compound contained in the dielectric layer arepreferably replaced with at least one element Re (yttrium (Y) or arare-earth element) selected from a group consisting of scandium (Sc),yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium(Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd),terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm),ytterbium (Yb) and lutetium (Lu).

The preferable amount of replacement by the element Re depends upon thevalue of the symbol m. For example, in the case where the symbol m isequal to 3, in the compositional formula: Bi₂A_((2−x))Re_(x)B₃O₁₂, x ispreferably equal to or larger than 0.4 and equal to or smaller than 1.8and more preferably equal to or larger than 1.0 and equal to or smallerthan 1.4. If the amount of replacement by the element Re is determinedwithin this range, the Curie temperature (phase transition temperaturefrom ferroelectric to paraelectric) of the dielectric layer can becontrolled preferably to be equal to or higher than −100° C. and equalto or lower than 100° C. and more preferably to be equal to or higherthan −50° C. and equal to or lower than 50° C. If the Curie point isequal to or higher than −100° C. and equal to or lower than 100° C. ,the dielectric constant of the dielectric thin film 6 increases. TheCurie temperature can be measured by DSC (differential scanningcalorimetry) or the like. If the Curie point becomes lower than roomtemperature (25° C.), tan δ further decreases and as a result, the lossvalue Q further increases.

Furthermore, in the case where the symbol m is equal to 4, in thecompositional formula: Bi₂A_((3−x))Re_(x)B₄O₁₅, x is preferably equal toor larger than 0.01 and equal to or smaller than 2.0 and more preferablyequal to or larger than 0.1 and equal to or smaller than 1.0.

Although the dielectric layer of the multi-layered unit according to thepresent invention has an excellent leak characteristic even if it doesnot contain the element Re, it is possible to further improve the leakcharacteristic by replacing part of the elements represented by thesymbols A or B with the element Re.

For example, even in the case where no part of the elements representedby the symbols A or B in the stoichiometric compositional formula of thebismuth layer structured compound is replaced with element Re, the leakcurrent measured at the electric filed strength of 50 kV/cm can becontrolled preferably to be equal to or lower than 1×10⁻⁷ A/cm² and morepreferably to be equal to or lower than 5×10⁻⁸ A/cm² and the shortcircuit ratio can be controlled preferably to be equal to or lower than10% and more preferably to be equal to or lower than 5%. However, in thecase where parts of the elements represented by the symbols A or B inthe stoichiometric compositional formula of the bismuth layer structuredcompound are replaced with element Re, the leak current measured underthe same condition can be controlled preferably to be equal to or lowerthan 5×10⁻⁸ A/cm² and more preferably to be equal to or lower than1×10⁻⁸ A/cm² and the short circuit ratio can be controlled preferably tobe equal to or lower than 5% and more preferably to be equal to or lowerthan 3%.

In the present invention, the dielectric layer can be formed using anyof various thin film forming processes such as a vacuum depositionprocess, a sputtering process, a pulsed laser deposition process (PLD),a metal organic chemical vapor deposition process (MOCVD), a chemicalsolution deposition process (CSD process) such as a metal-organicdecomposition process (MOD) and a sol-gel process or the like.Particularly, in the case where the dielectric layer has to be formed ata low temperature, a plasma CVD process, a photo-CVD process, a laserCVD process, a photo-CSD process, a laser CSD process or the like ispreferably used for forming the dielectric layer.

The multi-layered unit according to the present invention can be usednot only as a component of a thin film capacitor but also as a unit forcausing an inorganic EL device to emit light. Specifically, aninsulating layer is necessary between an electrode layer and aninorganic EL device in order to cause the inorganic EL device to emitlight. Since a dielectric layer of a dielectric material containing abismuth layer structured compound having an improved c axis orientationhas a high insulating property, it is possible to cause an inorganic ELdevice to emit light in a desired manner by disposing the inorganic ELdevice on the dielectric layer, disposing another electrode on theinorganic EL device and applying a voltage between the electrode layerand the other electrode.

The above and other objects and features of the present invention willbecome apparent from the following description made with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing schematically showing the structure of a bismuthlayer structured compound.

FIG. 2 is a schematic partial cross-sectional view showing amulti-layered unit which is a preferred embodiment of the presentinvention.

FIG. 3 is a schematic partial cross-sectional view showing a thin filmcapacitor fabricated using a multi-layered unit which is a preferredembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2 is a schematic partial cross-sectional view showing amulti-layered unit which is a preferred embodiment of the presentinvention.

As shown in FIG. 2, a multi-layered unit 1 according to this embodimentis constituted by laminating an electrode layer 3 and a dielectric layer4 on a support substrate 2 in this order.

In this embodiment, the support substrate 2 of the multi-layered unit 1is formed of fused quartz.

As shown in FIG. 2, the multi-layered unit 1 according to thisembodiment includes an electrode layer 3 on the support substrate 2.

In this embodiment, the electrode layer 3 is formed of BSCCO (bismuthstrontium calcium copper oxide) represented by the stoichiometriccompositional formula: Bi₂Sr₂CaCu₂O₈ and is oriented in the [001]direction.

The BSCCO (bismuth strontium calcium copper oxide) represented by thestoichiometric compositional formula: Bi₂Sr₂CaCu₂O₈ has an anisotropicproperty and conductivity and enables epitaxial growth of a dielectricmaterial containing a bismuth layer structured compound thereon.

Therefore, the electrode layer 3 can serve as an electrode and a bufferlayer for ensuring that a dielectric layer containing a bismuth layerstructured compound oriented in the [001] direction, namely, the c axisdirection, can be formed by epitaxially growing a dielectric materialcontaining the bismuth layer structured compound thereon.

In the case of directly forming an electrode layer made of platinum orthe like on the support substrate 2 made of fused quartz or the like,since the electrode layer tends to be oriented in the [111] direction,it is difficult to epitaxially grow a dielectric layer of a dielectricmaterial containing a bismuth layer structured compound on the electrodelayer and orient the bismuth layer structured compound in the [001]direction, namely, the c axis direction. However, in this embodiment,since the electrode layer 3 is formed of BSCCO (bismuth strontiumcalcium copper oxide) represented by the stoichiometric compositionalformula: Bi₂Sr₂CaCu₂O₈ and is formed of a material having an anisotropicproperty and conductivity and enabling epitaxial growth of a dielectricmaterial containing a bismuth layer structured compound thereon, theelectrode layer 3 can be oriented in the [001] direction. Therefore, itis possible to form a dielectric layer by epitaxially growing adielectric material containing a bismuth layer structured compound onthe electrode layer 3 and reliably orient the bismuth layer structuredcompound contained in the dielectric layer in the [001] direction,namely, the c axis direction.

In this embodiment, an electrode layer 3 containing BSCCO (bismuthstrontium calcium copper oxide) represented by the stoichiometriccompositional formula: Bi₂Sr₂CaCu₂O₈ is formed, for example, using apulsed laser deposition process (PLD).

When an electrode layer 3 containing BSCCO (bismuth strontium calciumcopper oxide) represented by the stoichiometric compositional formula:Bi₂Sr₂CaCu₂O₈ is to be formed using a pulsed laser deposition process(PLD), BSCCO (bismuth strontium calcium copper oxide) represented by thestoichiometric compositional formula: Bi₂Sr₂CaCu₂O₈ is used as a targetand the temperature of the barrier layer 3 of silicon oxide ismaintained at 650° C., thereby forming an electrode layer 3 having athickness of 100 nm and oriented in the [001] direction.

As shown in FIG. 2, the multi-layered unit 1 according to thisembodiment includes a dielectric layer 4 formed on the electrode layer3.

In this embodiment, the dielectric layer 4 is formed of a dielectricmaterial containing a bismuth layer structured compound represented bythe stoichiometric compositional formula: SrBi₄Ti₄O₁₅ wherein the symbolm is equal to 4 and the symbol A₃ is equal to Bi₂+Sr in the generalstoichiometric compositional formula of the bismuth layer structuredcompounds and having an excellent property as a capacitor material.

In this embodiment, the dielectric layer 4 is formed on the electrodelayer 3 using a metal organic deposition (MOD) process.

Concretely, a toluene solution of 2-ethyl hexanoate Sr, a 2-ethylhexanoate solution of 2-ethyl hexanoate Bi and a toluene solution of2-ethyl hexanoate Ti are stoichiometrically mixed so that the mixturecontains 1 mole of 2-ethyl hexanoate Sr, 4 moles of 2-ethyl hexanoate Biand 4 moles of 2-ethyl hexanoate Ti and is diluted with toluene. Theresultant constituent solution is coated on the electrode layer 3 usinga spin coating method and after drying the resultant dielectric layer 4is tentatively baked at a temperature under which the dielectric layer 4cannot be crystallized.

The same constituent solution is coated on the thus tentatively bakeddielectric layer 4 using a spin coating method to form a coating layerand the coating layer is dried and tentatively baked. These operationsare repeated.

When tentative baking is completed, the dielectric layer 4 is baked anda series of operations including coating, drying, tentative baking,coating, drying, tentative baking and baking are repeated until adielectric layer 4 having a required thickness, for example, 100 nm isobtained.

During these processes, a dielectric material containing a bismuth layerstructured compound is epitaxially grown and a dielectric layer 4oriented in the [001] direction, namely, the c axis direction is formed.

According to this embodiment, the multi-layered unit 1 has such astructure that the electrode layer 3 and the dielectric layer 4 arelaminated on the support substrate 2 formed of fused quartz and theelectrode layer 3 is formed of BSCCO (bismuth strontium calcium copperoxide) represented by the stoichiometric compositional formula:Bi₂Sr₂CaCu₂O₈, having an anisotropic property and conductivity andenabling epitaxial growth of a dielectric material containing a bismuthlayer structured compound thereon. Therefore, since the electrode layer3 serves as a buffer layer, it is possible to reliably form thedielectric layer 4 of a dielectric material containing a bismuth layerstructured compound oriented in the [001] direction, namely, the c axisdirection, by epitaxially growing the dielectric material containing thebismuth layer structured compound on the electrode layer 3.

Therefore, according to this embodiment, since the multi-layered unit 1includes the dielectric layer 4 formed of the dielectric materialcontaining the bismuth layer structured compound oriented in the [001]direction, namely, the c axis direction, in the case of, for example,providing an upper electrode on the dielectric layer 4 of themulti-layered unit 1 according to this embodiment, thereby fabricating athin film capacitor, and applying a voltage between the electrode layer3 and the upper electrode, the direction of an electric fieldsubstantially coincides with the c axis of the bismuth layer structuredcompound contained in the dielectric layer 4. As a result, since theferroelectric property of the bismuth layer structured compoundcontained in the dielectric layer 4 can be suppressed and theparaelectric property thereof can be fully exhibited, it is possible tofabricate a thin film capacitor having a small size and largecapacitance.

Further, according to this embodiment, since the multi-layered unit 1includes the dielectric layer 4 formed of the dielectric materialcontaining the bismuth layer structured compound oriented in the [001]direction, namely, the c axis direction, and the dielectric layer 4containing the bismuth layer structured compound whose c axisorientation is improved has a high insulating property, it is possibleto make the dielectric layer 4 thinner and therefore make a thin filmcapacitor much thinner

FIG. 3 is a schematic partial cross-sectional view showing a thin filmcapacitor fabricated using a multi-layered unit which is a preferredembodiment of the present invention.

As shown in FIG. 3, the thin film capacitor 10 includes themulti-layered unit 1 shown in FIG. 2 and an upper electrode 11 formed onthe dielectric layer 4 of the multi-layered unit 1.

In this embodiment, the support substrate 2 of the multi-layered unit 1serves to ensure the mechanical strength of the entire thin filmcapacitor 10.

Further, the electrode layer 3 of the multi-layered unit 1 serves as oneof electrodes of the thin film capacitor 10 and as a buffer layer fororienting the c axis of a bismuth layer structured compound contained inthe dielectric layer 4 substantially parallel to an electric field.

In this embodiment, the dielectric layer 4 of the multi-layered unit 1serves as a dielectric layer of the thin film capacitor 10.

In this embodiment, the upper electrode 11 serving as the other of theelectrodes of the thin film capacitor 10 is formed on the dielectriclayer 4 of the multi-layered unit 1.

The material for forming the upper electrode is not particularly limitedinsofar as it has conductivity and the upper electrode 11 can be formedof a metal such as platinum (Pt), ruthenium (Ru), rhodium (Rh),palladium (Pd), iridium (Ir), gold (Au), silver (Ag), copper (Cu),nickel (Ni) or the like, an alloy containing at least one of these metalas a principal component, a conductive oxide such as NdO, NbO, RhO₂,OsO₂, IrO₂, RuO₂, SrMoO₃, SrRuO₃, CaRuO₃, SrVO₃, SrCrO₃, SrCoO₃, LaNiO₃,Nb doped SrTiO₃ or the like or a mixture of these. Further, unlike theelectrode layer 3 of the multi-layered unit 1, since it is unnecessaryto consider the lattice mismatch with a material for forming thedielectric layer 4 when the material for forming the upper electrode 11is to be selected and it can be formed at the room temperature, theupper electrode 11 can be formed using a base metal such as iron (Fe),cobalt (Co) or the like or alloy such as WSi, MoSi or the like. Thethickness of the upper electrode 11 is not particularly limited insofaras it can serve as the other of the electrodes of the thin filmcapacitor 10 and the upper electrode 11 can be formed so as to have athickness of 10 to 10000 nm, for example.

The method for forming the upper electrode 11 is not particularlylimited and the upper electrode 11 can be formed using any of variousthin film forming processes such as a vacuum deposition process, asputtering process, a pulsed laser deposition process (PLD), a metalorganic chemical vapor deposition process (MOCVD), a chemical solutiondeposition process (CSD process) such as a metal-organic decompositionprocess (MOD) and a sol-gel process or the like. Among these, asputtering process is preferable from the viewpoint of formation speed.

In the thus constituted thin layer capacitor 10, the bismuth layerstructured compound contained in the dielectric layer 4 is oriented sothat the c axis thereof is substantially perpendicular to the electrodelayer 3 and the upper electrode 11. Therefore, when a voltage is appliedbetween the electrode layer 3 and the upper electrode 11, the directionof the electric field substantially coincides with the c axis of thebismuth layer structured compound contained in the dielectric layer 4.As a result, since the ferroelectric property of the bismuth layerstructured compound contained in the dielectric layer 6 can besuppressed and the paraelectric property thereof can be fully exhibited,it is possible to fabricate a thin film capacitor 10 having a small sizeand large capacitance.

A thin film capacitor 10 having such characteristics can be preferablyutilized as a decoupling capacitor, in particular, a decouplingcapacitor for an LSI having a high operating frequency.

The present invention has thus been shown and described with referenceto specific embodiments. However, it should be noted that the presentinvention is in no way limited to the details of the describedarrangements but changes and modifications may be made without departingfrom the scope of the appended claims.

For example, in the above described embodiments, the multi-layered unit1 is constituted by laminating on the support substrate 2, the electrodelayer 3 formed of BSCCO (bismuth strontium calcium copper oxide)represented by the stoichiometric compositional formula: Bi₂Sr₂CaCu₂O₈and the dielectric layer 4 formed of a dielectric material containing abismuth layer structured compound represented by the stoichiometriccompositional formula: SrBi₄Ti₄O₁₅ and having an excellent property as acapacitor material in this order. However, the multi-layered unit 1 maybe formed by further laminating a plurality of unit multi-layeredelements each including at least an electrode layer 3 and a dielectriclayer 4 on the dielectric layer 4 and a thin film capacitor may befabricated by forming an upper electrode on the dielectric layer 4 ofthe uppermost unit multi-layered element. However, in the case where themulti-layered unit 1 is constituted by further laminating a plurality ofunit multi-layered elements on the dielectric layer 4, if an electrodelayer included in each of the unit multi-layered elements is not formedby epitaxially growing crystals of a conductive material on a dielectriclayer 6, even if a dielectric material containing a bismuth layerstructured compound is epitaxially grown on the electrode layer, it isdifficult to orient the bismuth layer structured compound in the [001]direction and form a dielectric layer of the dielectric materialcontaining the bismuth layer structured compound oriented in the [001]direction. Therefore, it is required to form each unit multi-layeredelement so as to include an electrode layer, a buffer layer formed onthe electrode layer and a dielectric layer formed of a dielectricmaterial containing a bismuth layer structured compound on the bufferlayer. It is further possible to laminate one or more unit multi-layeredelements each including an electrode layer and a dielectric layer andone or more unit multi-layered elements each including an electrodelayer, a buffer layer formed on the electrode layer and a dielectriclayer formed of a dielectric material containing a bismuth is layerstructured compound on the buffer layer on the dielectric layer 4 in anarbitrary order and form an upper electrode on the dielectric layer 4 ofthe uppermost unit multi-layered element, thereby fabricating a thinfilm capacitor.

Further, in the above described embodiments, although the supportsubstrate 2 is formed of fused quartz, it is not absolutely necessary toemploy a support substrate 2 formed of fused quartz. The material forforming the support substrate 2 is not particularly limited insofar ascrystal cannot be epitaxially grown thereon. For example, instead of thesupport substrate 2 formed of fused quartz, another amorphous substratecan be used and further, a polycrystal substrate made of ceramic or thelike, a heat-resistant glass substrate, a resin substrate or the likecan be used as a support substrate.

Furthermore, in the above described embodiments, the multi-layered unit1 includes on the support substrate 2 the electrode layer 3 formed ofBSCCO (bismuth strontium calcium copper oxide) represented by thestoichiometric compositional formula: Bi₂Sr₂CaCu₂O₈ and serving as abuffer layer for epitaxially growing a dielectric material containing abismuth layer structured compound thereon. However, it is not absolutelynecessary to form the electrode layer 3 of BSCCO (bismuth strontiumcalcium copper oxide) represented by the stoichiometric compositionalformula: Bi₂Sr₂CaCu₂O₈ and the material for forming the electrode layer3 is not particularly limited insofar as it has an anisotropic propertyand conductivity and enables epitaxial growth of a dielectric materialcontaining a bismuth layer structured compound thereon. As a materialhaving an anisotropic property and conductivity and enabling epitaxialgrowth of a dielectric material containing a bismuth layer structuredcompound thereon, an oxide superconductor is preferably employed and acopper oxide superconductor having a CuO₂ plane is more preferablyemployed. Illustrative examples of copper oxide superconductors having aCuO₂ plane include BSCCO (bismuth strontium calcium copper oxide)represented by the stoichiometric compositional formula:Bi₂Sr₂Ca_(n−1)Cu_(n)O_(2n+4) and YBCO (yttrium barium copper oxide)represented by the stoichiometric compositional formula: YBa₂Cu₃O_(7−δ).

Moreover, in the above described embodiments, although the electrodelayer 3 of the multi-layered unit 1 is formed using a pulsed laserdeposition process (PLD), it is not absolutely necessary to form theelectrode layer 3 using a pulsed laser deposition process (PLD) and theelectrode layer 3 may be formed using any of various thin film formingprocesses such as a vacuum deposition process, a sputtering process, ametal organic chemical vapor deposition process (MOCVD), a chemicalsolution deposition process (CSD process) such as a metal-organicdecomposition process (MOD) and a sol-gel process or the like.

Further, in the above described embodiments, the multi-layered unit 1includes on the electrode layer 3 the dielectric layer 4 formed of adielectric material containing a bismuth layer structured compoundrepresented by the stoichiometric compositional formula: SrBi₄Ti₄O₁₅wherein the symbol m is equal to 4 and the symbol A₃ is equal to Bi₂+Srin the general stoichiometric compositional formula of the bismuth layerstructured compounds. However, it is not absolutely necessary to form onthe electrode layer 4 the dielectric layer 4 formed of a dielectricmaterial containing a bismuth layer structured compound represented bythe stoichiometric compositional formula: SrBi₄Ti₄O₁₅ wherein the symbolm is equal to 4 and the symbol A₃ is equal to Bi₂+Sr in the generalstoichiometric compositional formula of the bismuth layer structuredcompounds and the dielectric layer 4 may be formed of a dielectricmaterial containing a bismuth layer structured compound wherein m is notequal to 4 in the general stoichiometric compositional formula of abismuth layer structured compound. Further, the dielectric layer 4 maybe formed of a dielectric material containing another bismuth layerstructured compound having different constituent elements.

Furthermore, in the above described embodiments, although the dielectriclayer 4 is formed using a metal-organic decomposition process (MOD), itis not absolutely necessary to form the dielectric layer 4 using ametal-organic decomposition process and the dielectric layer 4 may beformed using some other thin film forming processes such as a vacuumdeposition process, a sputtering process, a pulsed laser depositionprocess (PLD), a metal organic chemical vapor deposition process(MOCVD), other chemical solution deposition process (CSD process) suchas a sol-gel process or the like.

Moreover, in the above described embodiments, although the multi-layeredunit 1 is used as a component of a thin film capacitor, themulti-layered unit 1 can be used not only as a component of a thin filmcapacitor but also as a multi-layered unit for causing an inorganic EL(electro-luminescence) device to emit light. Specifically, although aninsulating layer is necessary between an electrode layer 3 and aninorganic EL device in order to cause the inorganic EL device to emitlight, since a dielectric layer 4 of a dielectric material containing abismuth layer structured compound having an improved c axis orientationhas a high insulating property, it is possible to cause an inorganic ELdevice to emit light in a desired manner by disposing the inorganic ELdevice on the dielectric layer 6, disposing another electrode on theinorganic EL device and applying a voltage to the inorganic El device.

According to the present invention, it is possible to provide amulti-layered unit suitable for fabricating a thin film capacitor havinga small size and large capacitance and suitable for fabricating aninorganic EL (electro-luminescence) device capable of emitting lighthaving high luminescence.

1. A multi-layered unit constituted by forming on a support substrateformed of a material on which crystals cannot be epitaxially grown, anelectrode layer formed of a material having an anisotropic property andconductivity and enabling epitaxial growth of a dielectric materialcontaining a bismuth layer structured compound and oriented in the [001]direction, and an epitaxial dielectric layer containing a bismuth layerstructured compound on the electrode layer and oriented in the [001]direction in this order.
 2. A multi-layered unit in accordance withclaim 1 wherein the support substrate is formed of a material selectedfrom a group consisting of an amorphous substrate, a polycrystalsubstrate and a heat-resistant glass substrate.
 3. A multi-layered unitin accordance with claim 1 wherein the electrode layer is formed of anoxide superconductor.
 4. A multi-layered unit in accordance with claim 2wherein the electrode layer is formed of an oxide superconductor.
 5. Amulti-layered unit in accordance with claim 3 wherein the electrodelayer is formed of a copper oxide superconductor having a CuO₂ plane. 6.A multi-layered unit in accordance with claim 4 wherein the electrodelayer is formed of a copper oxide superconductor having a CuO₂ plane. 7.A multi-layered unit in accordance with claim 5 wherein the electrodelayer is formed of a copper oxide superconductor having a CuO₂ planeselected from a group consisting of BSCCO (bismuth strontium calciumcopper oxide) represented by the stoichiometric compositional formula:Bi₂Sr₂Ca_(n−1)Cu_(n)O_(2n+4) and YBCO (yttrium barium copper oxide)represented by the stoichiometric compositional formula: YBa₂Cu₃O₇−δ. 8.A multi-layered unit in accordance with claim 6 wherein the electrodelayer is formed of a copper oxide superconductor having a CuO₂ planeselected from a group consisting of BSCCO (bismuth strontium calciumcopper oxide) represented by the stoichiometric compositional formula:Bi₂Sr₂Ca_(n−1)Cu_(n)O_(2n+4) and YBCO (yttrium barium copper oxide)represented by the stoichiometric compositional formula: YBa₂Cu₃O₇−δ. 9.A multi-layered unit in accordance with claim 1 wherein the dielectriclayer contains a bismuth layer structured compound having a compositionrepresented by a stoichiometric compositional formula: (Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ or Bi₂A_(m−1)B_(m)O_(3m+3), where the symbol mis a natural number, the symbol A is at least one element selected froma group consisting of sodium (Na), potassium (K), lead (Pb), barium(Ba), strontium (Sr), calcium (Ca) and bismuth (Bi), and the symbol B isat least one element selected from a group consisting of iron (Fe),cobalt (Co), chromium (Cr), gallium (Ga), titanium (Ti), niobium (Nb),tantalum (Ta), antimony (Sb), vanadium (V), molybdenum (Mo) and tungsten(W) and when the symbol A and/or B includes two or more elements, theratio of the elements is arbitrarily determined.
 10. A multi-layeredunit in accordance with claim 2 wherein the dielectric layer contains abismuth layer structured compound having a composition represented by astoichiometric compositional formula: (Bi₂O₂)²⁺ (A_(m−1)B_(m)O_(3m+1))²⁻or Bi₂A_(m−1)B_(m)O_(3m+3), where the symbol m is a natural number, thesymbol A is at least one element selected from a group consisting ofsodium (Na), potassium (K), lead (Pb), barium (Ba), strontium (Sr),calcium (Ca) and bismuth (Bi), and the symbol B is at least one elementselected from a group consisting of iron (Fe), cobalt (Co), chromium(Cr), gallium (Ga), titanium (Ti), niobium (Nb), tantalum (Ta), antimony(Sb), vanadium (V), molybdenum (Mo) and tungsten (W) and when the symbolA and/or B includes two or more elements, the ratio of the elements isarbitrarily determined.
 11. A multi-layered unit in accordance withclaim 3 wherein the dielectric layer contains a bismuth layer structuredcompound having a composition represented by a stoichiometriccompositional formula: (Bi₂O₂)²⁺ (A_(m−1)B_(m)O_(3m+1))²⁻ orBi₂A_(m−1)B_(m)O_(3m+3), where the symbol m is a natural number, thesymbol A is at least one element selected from a group consisting ofsodium (Na), potassium (K), lead (Pb), barium (Ba), strontium (Sr),calcium (Ca) and bismuth (Bi), and the symbol B is at least one elementselected from a group consisting of iron (Fe), cobalt (Co), chromium(Cr), gallium (Ga), titanium (Ti), niobium (Nb), tantalum (Ta), antimony(Sb), vanadium (V), molybdenum (Mo) and tungsten (W) and when the symbolA and/or B includes two or more elements, the ratio of the elements isarbitrarily determined.
 12. A multi-layered unit in accordance withclaim 4 wherein the dielectric layer contains a bismuth layer structuredcompound having a composition represented by a stoichiometriccompositional formula: (Bi₂O₂)²⁺ (A_(m−1)B_(m)O_(3m+1))²⁻ orBi₂A_(m−1)B_(m)O_(3m+3), where the symbol m is a natural number, thesymbol A is at least one element selected from a group consisting ofsodium (Na), potassium (K), lead (Pb), barium (Ba), strontium (Sr),calcium (Ca) and bismuth (Bi), and the symbol B is at least one elementselected from a group consisting of iron (Fe), cobalt (Co), chromium(Cr), gallium (Ga), titanium (Ti), niobium (Nb), tantalum (Ta), antimony(Sb), vanadium (V), molybdenum (Mo) and tungsten (W) and when the symbolA and/or B includes two or more elements, the ratio of the elements isarbitrarily determined.
 13. A multi-layered unit in accordance withclaim 5 wherein the dielectric layer contains a bismuth layer structuredcompound having a composition represented by a stoichiometriccompositional formula: (Bi₂O₂)²⁺ (A_(m−1)B_(m)O_(3m+1))²⁻ orBi₂A_(m−1)B_(m)O_(3m+3), where the symbol m is a natural number, thesymbol A is at least one element selected from a group consisting ofsodium (Na), potassium (K), lead (Pb), barium (Ba), strontium (Sr),calcium (Ca) and bismuth (Bi), and the symbol B is at least one elementselected from a group consisting of iron (Fe), cobalt (Co), chromium(Cr), gallium (Ga), titanium (Ti), niobium (Nb), tantalum (Ta), antimony(Sb), vanadium (V), molybdenum (Mo) and tungsten (W) and when the symbolA and/or B includes two or more elements, the ratio of the elements isarbitrarily determined.
 14. A multi-layered unit in accordance withclaim 6 wherein the dielectric layer contains a bismuth layer structuredcompound having a composition represented by a stoichiometriccompositional formula: (Bi₂O₂)²⁺ (A_(m−1)B_(m)O_(3m+1))²⁻ orBi₂A_(m−1)B_(m)O_(3m+3), where the symbol m is a natural number, thesymbol A is at least one element selected from a group consisting ofsodium (Na), potassium (K), lead (Pb), barium (Ba), strontium (Sr),calcium (Ca) and bismuth (Bi), and the symbol B is at least one elementselected from a group consisting of iron (Fe), cobalt (Co), chromium(Cr), gallium (Ga), titanium (Ti), niobium (Nb), tantalum (Ta), antimony(Sb), vanadium (V), molybdenum (Mo) and tungsten (W) and when the symbolA and/or B includes two or more elements, the ratio of the elements isarbitrarily determined.
 15. A multi-layered unit in accordance withclaim 7 wherein the dielectric layer contains a bismuth layer structuredcompound having a composition represented by a stoichiometriccompositional formula: (Bi₂O₂)²⁺ (A_(m−1)B_(m)O_(3m+1))²⁻ orBi₂A_(m−1)B_(m)O_(3m+3), where the symbol m is a natural number, thesymbol A is at least one element selected from a group consisting ofsodium (Na), potassium (K), lead (Pb), barium (Ba), strontium (Sr),calcium (Ca) and bismuth (Bi), and the symbol B is at least one elementselected from a group consisting of iron (Fe), cobalt (Co), chromium(Cr), gallium (Ga), titanium (Ti), niobium (Nb), tantalum (Ta), antimony(Sb), vanadium (V), molybdenum (Mo) and tungsten (W) and when the symbolA and/or B includes two or more elements, the ratio of the elements isarbitrarily determined.
 16. A multi-layered unit in accordance withclaim 8 wherein the dielectric layer contains a bismuth layer structuredcompound having a composition represented by a stoichiometriccompositional formula: (Bi₂O₂)²⁺ (A_(m−1)B_(m)O_(3m+1))²⁻ orBi₂A_(m−1)B_(m)O_(3m+3), where the symbol m is a natural number, thesymbol A is at least one element selected from a group consisting ofsodium (Na), potassium (K), lead (Pb), barium (Ba), strontium (Sr),calcium (Ca) and bismuth (Bi), and the symbol B is at least one elementselected from a group consisting of iron (Fe), cobalt (Co), chromium(Cr), gallium (Ga), titanium (Ti), niobium (Nb), tantalum (Ta), antimony(Sb), vanadium (V), molybdenum (Mo) and tungsten (W) and when the symbolA and/or B includes two or more elements, the ratio of the elements isarbitrarily determined.
 17. A multi-layered unit in accordance withclaim 1 further comprises an upper electrode layer overlying thedielectric layer.
 18. The multi-layered unit in accordance with claim 17wherein the upper electrode layer is platinum (Pt), ruthenium (Ru),rhodium (Rh), palladium (Pd), iridium (Ir), gold (Au), silver (Ag),copper (Cu), nickel (Ni), an alloy thereof, NdO, NbO, RhO₂, OsO₂, IrO₂,RuO₂, SrMoO₃, SrRuO₃, CaRuO₃, SrVO₃, SrCrO₃, SrCoO₃, LaNiO₃, Nb dopedSrTiO₃ or a mixture thereof.
 19. A multi-layered unit comprising: asupport substrate of a material upon which crystals cannot beepitaxially grown; a conductive lower electrode layer overlying thesupport substrate, said lower electrode layer having an anisotropicproperty and capable of allowing epitaxial growth of a dielectricmaterial; and an epitaxial dielectric material overlying the lowerelectrode, said dielectric material having a crystal structure andcontaining a bismuth layer structured compound oriented in the [001]direction of the crystal structure.
 20. The multi-layered unit of claim19 wherein the lower electrode layer is formed directly on and incontact with the support substrate and said dielectric material isformed directly on and in contact with the lower electrode layer. 21.The multi-layered unit of claim 20 wherein the lower electrode layercomprises a copper oxide superconductor having a CuO₂ plane.
 22. Themulti-layered unit of claim 21 wherein the lower electrode layercomprises a copper oxide superconductor having a CuO₂ plane selectedfrom a group consisting of BSCCO (bismuth strontium calcium copperoxide) represented by the stoichiometric compositional formula:Bi₂Sr₂Ca_(n−1)Cu_(n)O_(2n+4) and YBCO (yttrium barium copper oxide)represented by the stoichiometric compositional formula: YBa₂Cu₃O₇−δ.23. The multi-layered unit of claim 19 wherein the dielectric layercontains a bismuth layer structured compound having a compositionrepresented by a stoichiometric compositional formula: (Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ or Bi₂A_(m−1)B_(m)O_(3m+3), where the symbol mis a natural number, the symbol A is at least one element selected froma group consisting of sodium (Na), potassium (K), lead (Pb), barium(Ba), strontium (Sr), calcium (Ca) and bismuth (Bi), and the symbol B isat least one element selected from a group consisting of iron (Fe),cobalt (Co), chromium (Cr), gallium (Ga), titanium (Ti), niobium (Nb),tantalum (Ta), antimony (Sb), vanadium (V), molybdenum (Mo) and tungsten(W) and when the symbol A and/or B includes two or more elements, theratio of the elements is arbitrarily determined.
 24. The multi-layeredunit of claim 19 further comprising an upper conductive electrode layeroverlying the dielectric layer.
 25. The multi-layered unit of claim 24wherein the upper conductive electrode layer is platinum (Pt), ruthenium(Ru), rhodium (Rh), palladium (Pd), iridium (Ir), gold (Au), silver(Ag), copper (Cu), nickel (Ni), an alloy thereof, NdO, NbO, RhO₂, OsO₂,IrO₂, RuO₂, SrMoO₃, SrRuO₃, CaRuO₃, SrVO₃, SrCrO₃, SrCoO₃, LaNiO₃, Nbdoped SrTiO₃ or a mixture thereof.
 26. A thin film capacitor comprising:a support substrate of a material upon which crystals cannot beepitaxially grown; a plurality of multi-layer units formed on top of thesupport substrate, each of said multi-layer units including a conductivefirst electrode layer having an anisotropic property and capable ofallowing epitaxial growth of an epitaxial dielectric material, and anepitaxial dielectric material overlying the first electrode layer, saiddielectric material having a crystal structure and containing a bismuthlayer structured compound oriented in the [001] direction of the crystalstructure; and a second electrode layer overlying the plurality ofmulti-layer units.
 27. The thin film capacitor of claim 26 wherein eachof the plurality of the multi-layer units overlies on top of one anotherto form a stack.
 28. The thin film capacitor of claim 27 wherein each ofthe first electrode layers includes a copper oxide superconductor havinga CuO₂ plane.
 29. The thin film capacitor of claim 28 wherein each ofthe first electrode layers includes a copper oxide superconductor havinga CuO₂ plane selected from a group consisting of BSCCO (bismuthstrontium calcium copper oxide) represented by the stoichiometriccompositional formula: Bi₂Sr₂Ca_(n−1)Cu_(n)O_(2n+4) and YBCO (yttriumbarium copper oxide) represented by the stoichiometric compositionalformula: YBa₂Cu₃O₇−δ.
 30. The thin film capacitor of claim 26 whereineach of the dielectric layers contains, independently of each other, abismuth layer structured compound having a composition represented by astoichiometric compositional formula: (Bi₂O₂)²⁺ (A_(m−1)B_(m)O_(3m+1))²⁻or Bi₂A_(m−1)B_(m)O_(3m+3), where the symbol m is a natural number, thesymbol A is at least one element selected from a group consisting ofsodium (Na), potassium (K), lead (Pb), barium (Ba), strontium (Sr),calcium (Ca) and bismuth (Bi), and the symbol B is at least one elementselected from a group consisting of iron (Fe), cobalt (Co), chromium(Cr), gallium (Ga), titanium (Ti), niobium (Nb), tantalum (Ta), antimony(Sb), vanadium (V), molybdenum (Mo) and tungsten (W) and when the symbolA and/or B includes two or more elements, the ratio of the elements isarbitrarily determined.
 31. The thin film capacitor of claim 26 whereinthe second electrode layer is platinum (Pt), ruthenium (Ru), rhodium(Rh), palladium (Pd), iridium (Ir), gold (Au), silver (Ag), copper (Cu),nickel (Ni), an alloy thereof, NdO, NbO, RhO₂, OsO₂, IrO₂, RuO₂, SrMoO₃,SrRuO₃, CaRuO₃, SrVO₃, SrCrO₃, SrCoO₃, LaNiO₃, Nb doped SrTiO₃ or amixture thereof.